Method for manufacturing a semiconductor device

ABSTRACT

In a method of manufacturing a semiconductor device, a first layer having an opening is formed over a substrate. A second layer is formed over the first layer and the substrate. A photo resist pattern is formed over the second layer above the opening of the first layer. The photo resist pattern is reflowed by a thermal process. An etch-back operation is performed to planarize the second layer.

RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/726,085 filed Aug. 31, 2018, the entire content of which isincorporated herein by reference.

BACKGROUND

As the semiconductor industry has progressed into nanometer technologyprocess nodes in pursuit of higher device density, higher performance,and lower costs, challenges from both fabrication and design issuesbecome greater. Lithography operations are one of the key operations inthe semiconductor manufacturing process. In the lithography operations,flatness or unevenness of the underlying structure is important becauseof a tight focus margin in the lithography operations. Accordingly, itis necessary to planarize uneven underlying structures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 shows a cross sectional view of one of the various stages of asequential semiconductor device manufacturing process according to anembodiment of the present disclosure.

FIG. 2 shows a cross sectional view of one of the various stages of asequential semiconductor device manufacturing process according to anembodiment of the present disclosure.

FIG. 3 shows a cross sectional view of one of the various stages of asequential semiconductor device manufacturing process according to anembodiment of the present disclosure.

FIG. 4A shows a cross sectional view and FIG. 4B shows a schematic planview of one of the various stages of a sequential semiconductor devicemanufacturing process according to an embodiment of the presentdisclosure.

FIG. 5A shows a cross sectional view and FIG. 5B shows a schematic planview of one of the various stages of a sequential semiconductor devicemanufacturing process according to an embodiment of the presentdisclosure. FIG. 5C shows a cross sectional view of one of the variousstages of a sequential semiconductor device manufacturing processaccording to another embodiment of the present disclosure.

FIG. 6A shows a cross sectional view and FIG. 6B shows a schematic planview of one of the various stages of a sequential semiconductor devicemanufacturing process according to an embodiment of the presentdisclosure.

FIG. 7 shows a cross sectional view of one of the various stages of asequential semiconductor device manufacturing process according to anembodiment of the present disclosure.

FIG. 8A shows a cross sectional view and FIG. 8B shows a schematic planview of one of the various stages of a sequential semiconductor devicemanufacturing process according to an embodiment of the presentdisclosure.

FIGS. 9 and 10 show plan views of one of the various stages of asequential semiconductor device manufacturing process according toembodiments of the present disclosure.

FIG. 11 shows a cross sectional view of a semiconductor device accordingto embodiments of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The device may be otherwise oriented (rotated 90 degrees orat other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“made of” may mean either “comprising” or “consisting of.” Further, inthe following fabrication process, there may be one or more additionaloperations in between the described operations, and the order ofoperations may be changed. In the present disclosure, the phrase “atleast one of A, B and C” means either one of A, B, C, A+B, A+C, B+C orA+B+C, and does not mean one from A, one from B and one from C, unlessotherwise explained.

The semiconductor devices include interconnect structures that include aplurality of interconnect pattern (line) layers having conductivepatterns and a plurality of contact holes/vias for connecting variousfeatures in one portion/feature of a semiconductor chip (die) to otherportions/features of the chip. The interconnect and via structures areformed of conductive materials such as metal, and the semiconductordevices include several interconnect layers in various embodiments.

The interconnect layer patterns in different layers are also coupled toone another through vias that extend vertically between one or severalinterconnect layers. The interconnect layer patterns are coupled toexternal features and can represent bit lines, signal lines, word lines,and various input/output connections in some embodiments. In someembodiments of the disclosure, each of the interconnect structures isformed by a damascene process, in which a layer of an inter-metaldielectric (IMD) material is deposited, trenches and vias are formed andfilled with a conductive material (e.g., copper or aluminum or variousalloys) and the surface is planarized by a planarization operation, suchas a resist etch-back process and a chemical mechanical polishing (CMP)process, although other patterning techniques are used in otherembodiments. Because of the resolution limit of photolithographyprocesses, multiple patterning lithography processes are used to formdensely arranged interconnects and/or vias.

In the lithography operations, flatness of the underlyinglayer/structure is critical because of a tight focus margin.Accordingly, when the underlying layer/structure is uneven, it isnecessary to planarize the unevenness with one or more planarizationlayers before applying a photo resist.

A resist etch-back operation is one of the planarization operations.After a film, such as a dielectric film, is formed over an unevensurface, such as a gate structure, a fin structure and/or a wiringstructure, a photo resist layer is coated on the film. The photo resistlayer is then exposed to an exposure light (e.g., deep ultra violet(DUV) light or extreme ultra violet (EUV) light) and exposed photoresist layer is developed to form a resist pattern. In the etch-backprocess, the resist pattern remains in an area having a lower surfaceheight. Then, the resist pattern and the underlying film arepreferentially etched together to remove a thick portion of the film.

However, when there is a space between a high portion of an unevensurface and the resist pattern or an overlap between the high portion ofthe uneven surface and the resist pattern, a gap or a protrusion mayoccur after the etch-back process. The embodiments of the presentdisclosure resolve such a problem.

FIGS. 1-8B show views of the various stages of a sequentialsemiconductor device manufacturing process according to embodiments ofthe present disclosure. It is understood that additional operations canbe provided before, during, and after processes shown by FIGS. 1-8B, andsome of the operations described below can be replaced or eliminated,for additional embodiments of the method. The order of theoperations/processes may be interchangeable. In FIGS. 4A-6B, 8A and 8B,the “A” figures show cross sectional views and the “B” figures show topviews (plan views).

As shown in FIG. 1, a first layer 20 is formed over an underlying layer10. In some embodiments, the underlying layer 10 is a semiconductorsubstrate. In one embodiment, the substrate 10 is a silicon substrate.Alternatively, the substrate may comprise another elementarysemiconductor, such as germanium; a compound semiconductor includingGroup IV-IV compound semiconductors such as SiC and SiGe, Group III-Vcompound semiconductors such as GaAs, GaP, GaN, InP, InAs, InSb, GaAsP,AlGaN, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinationsthereof. Amorphous substrates, such as amorphous Si or amorphous SiC, oran insulating material, such as silicon oxide may also be used as thesubstrate. The substrate may include various regions that have beensuitably doped with impurities (e.g., p-type or n-type conductivity).

In other embodiments, the underlying layer 10 includes one or morelayers of a dielectric material or a conductive material. The dielectricmaterial includes silicon oxide, silicon nitride, silicon oxynitride(SiON), SiOCN, SiCO, SiCN, fluorine-doped silicate glass (FSG), or alow-k dielectric material, or any other suitable dielectric materials.The dielectric material layer may be formed by chemical vapor deposition(CVD), physical vapor deposition (PVD), atomic layer deposition (ALD),or other suitable film forming processes. In some embodiments, after thedielectric layer is formed, a planarization process, such as an etchback process and/or a chemical mechanical polishing (CMP) process isperformed on the dielectric layer.

The conductive material includes a semiconductor material, such as anelementary semiconductor including silicon or germanium; Group IV-IVcompound semiconductors; or Group III-V compound semiconductors as setforth above. The semiconductor material can be poly crystalline,amorphous or crystalline. The conductive material also includes metallicmaterial, such as Al, Cu, AlCu, W, Co, Ti, Ta, Ni, a silicide, TiN orTaN, or any suitable materials. The conductive material can be formed byCVD, PVD, ALD, molecular beam epitaxy (MBE), electro plating, or othersuitable film forming processes.

In some embodiments, the first layer 20 includes one or more layers of adielectric material or a conductive material. The dielectric materialfor the first layer 20 includes silicon oxide, silicon nitride, siliconoxynitride (SiON), SiOCN, SiCO, SiCN, fluorine-doped silicate glass(FSG), or a low-k dielectric material, or any other suitable dielectricmaterials. The conductive material for the second layer includesmetallic material, such as Al, Cu, AlCu, W, Co, Ti, Ta, Ni, Mo, or alloythereof, a silicide, TiN or TaN, or any suitable materials. The firstlayer 20 can be formed by CVD, PVD, ALD, molecular beam epitaxy (MBE),electro plating, or other suitable film forming processes. In oneembodiments, the first layer 20 is a metal or metallic layer.

After the first layer 20 is formed, by using one or more lithography andetching operations, the first layer 20 is patterned to have one or morefirst layer patterns 22 and one or more openings 24, as shown in FIG. 2.In the opening 24, the underlying layer 10 is exposed.

A thickness T1 of the first layer 20, when made of a conductivematerial, is in a range from about 10 nm to about 1000 nm in someembodiments, and in in a range from about 50 nm to about 500 nm in otherembodiments. The thickness T1 of the first layer 20, when made of adielectric material, is in a range from about 50 nm to about 2000 nm insome embodiments, and in in a range from about 100 nm to about 500 nm inother embodiments. In some embodiments, an edge of the first layerpattern 22 has a slope. In some embodiments, the slope angle θ1 measuredfrom the upper surface of the underlying layer 10 is in a range fromabout 45° to about 90° and is in a range from about 70° to about 85° inother embodiments.

Then, as shown in FIG. 3, a second layer 30 is formed over the patternedfirst layer 20 and the underlying layer 10. In some embodiments, thesecond layer 30 includes one or more layers of a dielectric material ora conductive material. When the first layer 20 is made of a dielectricmaterial, the second layer 30 is made of a conductive material, and whenthe first layer 20 is made of a conductive material, the second layer 30is made of a dielectric material, in some embodiments. The dielectricmaterial for the second layer 30 includes silicon oxide, siliconnitride, silicon oxynitride (SiON), SiOCN, SiCO, SiCN, fluorine-dopedsilicate glass (FSG), or a low-k dielectric material, or any othersuitable dielectric materials. The conductive material includes metallicmaterial, such as Al, Cu, AlCu, W, Co, Ti, Ta, Ni, Mo, or alloy thereof,silicide, TiN or TaN, or any suitable materials. The second layer 30 canbe formed by CVD, PVD, ALD, molecular beam epitaxy (MBE), electroplating, or other suitable film forming processes. In one embodiments,the second layer 30 is a dielectric material layer. A thickness T2 ofthe second layer 30 when made of a dielectric material, is in a rangefrom about 50 nm to about 2000 nm in some embodiments, and is in a rangefrom about 100 nm to about 500 nm in other embodiments. The thickness T2of the second layer 30, when made of a conductive material, is in arange from about 10 nm to about 1000 nm in some embodiments, and is in arange from about 50 nm to about 500 nm in other embodiments.

As shown in FIG. 3, a step 32 caused by the first layer pattern 22 isformed in the second layer 30 between an upper surface 33 above thefirst layer pattern 22 and a lower surface 34 above the opening 24 ofthe first layer 20. The height T3 of the step 32 is substantially equalto the thickness of the first layer 20 in some embodiments.

Then, by using one or more lithography operations, a photo resistpattern 40 is formed over the second layer 30 above the opening 24 ofthe first layer 20, as shown in FIGS. 4A and 4B. In FIG. 4B, theunderlying first layer pattern 22, which is covered by the second layer30 is shown.

The photo resist layer is a photosensitive layer that is patterned byexposure to actinic radiation. Typically, the chemical properties of thephotoresist regions struck by incident radiation change in a manner thatdepends on the type of photoresist used. A photo resist layer istypically a positive resist or a negative resist. The positive resistrefers to a photoresist material that when exposed to radiation(typically UV light) becomes soluble in a developer, such as atetramethylammonium hydroxide (TMAH) solution, while the region of thephotoresist that is non-exposed (or exposed less) is insoluble in thedeveloper. Negative resist, on the other hand, refers to a photoresistmaterial that when exposed to radiation becomes insoluble in thedeveloper, while the region of the photoresist that is non-exposed (orexposed less) is soluble in the developer. The region of a negativeresist that becomes insoluble upon exposure to radiation may becomeinsoluble due to a cross-linking reaction caused by the exposure toradiation.

In some embodiments, the photo resist is a chemically amplified photoresist. When a positive tone chemically amplified resist is used, acidgenerated by the exposure light from a photo acid generator (PAG) in thephoto resist cleaves acid-cleavable polymers in the photo resist duringthe post-exposure baking. After the acid cleaves the polymer, thepolymer becomes more hydrophilic (i.e., soluble in an aqueousdeveloper). After the polymer becomes more hydrophilic, the polymercannot be dissolved by organic solvent, for example, normal butylacetate, but can be dissolved by a basic solution, for example, 2.38%tetramethylammonium hydroxide (TMAH) solution.

When a negative tone chemically amplified resist is used, acid generatedby the exposure light from a photo acid generator (PAG) in the photoresist catalyzes a cross-linking reaction of acid catalyzed crosslinkable polymer in the photo resist or causes polymeric pinacol in thephoto resist to undergo pinacol rearrangement, during the post-exposurebaking. After the polymer cross linking or the undergoing of pinacolrearrangement, the polymers become more hydrophobic. After the polymerbecome more hydrophobic, the polymers are not dissolved by a basicdeveloping solution, for example, 2.38% TMAH solution.

In some embodiments, the photo resist includes one or more polymerresins and a photo active compound (PAC). In some embodiments, thepolymer resin includes a hydrocarbon structure (such as an alicyclichydrocarbon structure) that contains one or more groups that willdecompose (e.g., acid labile groups or acid leaving groups) or otherwisereact when mixed with acids, bases, or free radicals generated by thePACs. In some embodiments, the hydrocarbon structure includes arepeating unit that forms a skeletal backbone of the polymer resin. Thisrepeating unit may include acrylic esters, methacrylic esters, crotonicesters, vinyl esters, maleic diesters, fumaric diesters, itaconicdiesters, (meth)acrylonitrile, (meth)acrylamides, styrenes, vinylethers, combinations of these, or the like.

The PACs are photoactive components, such as photoacid generators(PAGs), photobase generators, free-radical generators, or the like. ThePACs may be positive-acting or negative-acting. In some embodiments, thePACs include halogenated triazines, onium salts, diazonium salts,aromatic diazonium salts, phosphonium salts, sulfonium salts, iodoniumsalts, imide sulfonate, oxime sulfonate, diazodisulfone, disulfone,o-nitrobenzylsulfonate, sulfonated esters, halogenated sulfonyloxydicarboximides, diazodisulfones, α-cyanooxyamine-sulfonates,imidesulfonates, ketodiazosulfones, sulfonyldiazoesters,1,2-di(arylsulfonyl)hydrazines, nitrobenzyl esters, and the s-triazinederivatives, combinations of these, or the like. The group which willdecompose, otherwise known as a leaving group or, in some embodiments inwhich the PAC is a photoacid generator (PAG), an acid labile group, isattached to the hydrocarbon structure so that, it will react with theacids/bases/free radicals generated by the PACs during exposure. In someembodiments, the group which will decompose is a carboxylic acid group,a fluorinated alcohol group, a phenolic alcohol group, a sulfonic group,a sulfonamide group, a sulfonylimido group, an (alkylsulfonyl)(alkylcarbonyl)methylene group, an (alkylsulfonyl)(alkyl-carbonyl)imidogroup, a bis(alkylcarbonyl)methylene group, a bis(alkylcarbonyl)imidogroup, a bis(alkylsylfonyl)methylene group, a bis(alkylsulfonyl)imidogroup, a tris(alkylcarbonyl methylene group, atris(alkylsulfonyl)methylene group, combinations of these, or the like.Specific groups that are used for the fluorinated alcohol group includefluorinated hydroxyalkyl groups, such as a hexafluoroisopropanol groupin some embodiments. Specific groups that are used for the carboxylicacid group include acrylic acid groups, methacrylic acid groups, or thelike. Other suitable materials are included in a photo sensitive siliconcontaining layer.

A photo resist layer is spin-coated on the second layer 30, and thephoto resist layer is exposed with an exposure light/beam through aphoto mask. The exposure light/beam can be deep ultra violet (DUV)light, such as KrF excimer laser light and ArF excimer laser light,extreme ultra violet (EUV) light having a wavelength around 13.5 nm, anX-ray, and/or electron beam. In some embodiments, multiple exposureprocesses are applied. After development of the exposed photo resist,the photo resist pattern 40 is obtained.

A thickness T4 of the photo resist pattern 40 is in a range from about100 nm to about 1000 nm in some embodiments, and is in a range fromabout 200 nm to about 700 nm in other embodiments. A distance D1 betweenthe edge of the first layer pattern 22 (closest to the photo resistpattern 40) and the edge of the photo resist pattern 40 (closest to thefirst layer pattern 22) is in a range from about 100 nm to about 2000 nmin some embodiments, and in in a range from about 600 nm to about 1000nm in other embodiments.

Then, as shown in FIGS. 5A and 5B, the photo resist pattern 40 issubjected to a thermal reflow process. The substrate with the photoresist pattern 40 is heated at a temperature in a range from about 150°C. to about 200° C. in some embodiments, and in a range from about 170°C. to about 180° C. in other embodiments. The reflow process isperformed by using a hot plate, on which the substrate is placed, insome embodiments. The reflow time is in a range from about 30 seconds toabout 120 seconds in some embodiments, and is in a range from about 40seconds to about 80 seconds in other embodiments. The photo resist has aglass transition temperature in a range from about 80° C. to about 100°C. in some embodiments. In other embodiments, the reflow process is aninfrared lamp annealing process.

After the thermal reflow process, the edge of the reflowed photo resistpattern 42 is located at near the edge of the first layer pattern 22, asshown in FIGS. 5A and 5B. Due to a surface tension of the flowing photoresist, reflowing the photo resist pattern 40 substantially stops at thestep 32 formed in the second layer 30 caused by the first layer pattern22, in a self-aligning manner. Thus, no reflowed photo resist isdisposed over the upper surface 33 of the second layer 30 above thefirst layer pattern 22 in some embodiments. In some embodiments, thereflowed photo resist pattern 42 fully covers the sidewall of the step32. In other embodiments, an upper portion (e.g., 0-20% of the stepheight) of the sidewall of the step 32 is not covered by the reflowedphoto resist pattern 42.

In other embodiments, the reflowed photo resist 42 is disposed over theupper surface 33 of the second layer 30 above the first layer pattern22, as shown in FIG. 5C. In some embodiments, a lateral end of thereflowed photo resist 42 is located just above the sidewall of the edgeportion of the first layer pattern 22. In other embodiments, the lateralend of the reflowed photo resist 42 is located over the flat surface ofthe first layer pattern 22. A distance D2 between the edge of the firstlayer pattern 22 and the lateral end of the reflowed photo resistpattern 42 is in a range from about 10 nm to about 500 nm in someembodiments, and is in a range from about 50 nm to about 200 nm in otherembodiments.

In some embodiments, the reflowed photo resist pattern 42 after thereflow process overlaps the first layer pattern 22 in plan view. Theoverlap amount is in a range from about 10 nm to about 200 nm in someembodiments, and is in a range from about 10 nm to about 100 nm in otherembodiments. In some embodiments, the edge of the reflowed photo resistpattern 42 after the reflow process is spaced apart from the edge of thefirst layer pattern 22 in plan view. A distance between the edge of thereflowed photo resist pattern 42 and the edge of the first layer pattern22 is in a range from about 10 nm to about 200 nm in some embodiments,and is in a range from about 20 nm to about 100 nm in other embodiments.

In some embodiments, the reflow amount, which is a distance between theoriginal edge of the photo resist pattern 40 shown in FIG. 4A and thelateral end of the reflowed photo resist 42 shown in FIG. 5A or 5C is ina range from about 100 nm to about 2000 nm, and in in a range from about600 nm to about 1000 nm in other embodiments.

As shown in FIG. 5A, the tangent line and the line parallel to thesurface of the underlying layer 10 or the substrate (horizontal line)has an angle θ2 at the step 32. In some embodiments, the angle θ is in arange from about 5° to about 30°, and is in a range from about 10° toabout 20° in other embodiments.

Then, as shown in FIGS. 6A and 6B, one or more etching operations areperformed to planarize the second layer 30. The etching operation (i.e.,an etch-back operation) includes plasma dry etching in some embodiments.The etch-back operation is performed such that an etching rate of thereflowed photo resist pattern 42 is faster than an etching rate of thesecond layer 30 in some embodiments. The etching condition may bechanged during the etch-back operation.

As shown in FIG. 6A, the etching is stopped when the height of thesecond layer 30 over the first layer pattern 22 is substantially equalto, e.g., ±10% of, the height of the second layer 30 above the opening24 of the first layer 20. In some embodiments, a residual photo resistpattern 44 remains, which is removed after the etch-back operation byone or more resist ashing and/or cleaning operations.

After the etch-back operation (planarization etching), in someembodiments, a protrusion 50 of the second layer having a height H1 isformed, as shown in FIG. 7. The height H1 is in a range from about 10 nmto about 100 nm in some embodiments, and is in a range from about 30 nmto about 60 nm in other embodiments. In some embodiments, the protrusionis asymmetric as shown in FIG. 7 in the cross section. For example, oneside has a smooth gradual slope and the other side has a steep slope insome embodiments.

FIGS. 8A and 8B show the structure after the residual photo resist layer44 is removed. In some embodiments, the protrusion 55 has a line shapealong the edge of the first layer pattern 22 in plan view, as shown inFIG. 8B. In some embodiments, a distance D3 between the edge of thefirst layer pattern 22 and the top (apex) of the protrusion 50 is in arange from about 0 nm to about 100 nm in some embodiments, and is in arange from about 10 nm to about 50 nm in other embodiments. In someembodiments, the top of the protrusion 50 is located above the firstlayer pattern 22. In certain embodiments, the top of the protrusion 50is located above the sidewall of the edge portion of the first layerpattern 22. In some embodiments, one or more additional planarizationoperations, such as an etch-back operation and a CMP operation, areperformed to remove the protrusion or to reduce the height of theprotrusion.

FIG. 9 shows a plan view of a pattern layout according to an embodimentof the present disclosure. As shown in FIG. 9, the first layer includesfour first layer patterns 21, 23, 25 and 27. An opening is formed by thefirst layer patterns 21, 23, 25 and 27 surrounding the center area. Thephoto resist pattern 45 is formed in the opening surrounded by the firstlayer patterns.

In some embodiments, the photo resist pattern 45 has a rectangular shapehaving a short side width W1 (along the X direction) and a long sidelength L1 (along the Y direction) as shown in FIG. 9 (W1<L1). Further,as designed, a space having a distance S1 is formed between the longside of the photo resist pattern 45 and the first layer pattern 21 (or23), and a space having a distance S2 is formed between the short sideof the photo resist pattern 45 and the first layer pattern 25 (or 27),as shown in FIG. 9. In some embodiments, S1 is different from S2 and incertain embodiments, S1 is smaller than S2.

FIG. 10 shows a plan view of a pattern layout according to anotherembodiment of the present disclosure. As shown in FIG. 10, the firstlayer 20 includes four first layer patterns 21, 23, 25 and 27. Anopening is formed by the first layer patterns 21, 23, 25 and 27surrounding the center area. The photo resist pattern 47 is formed inthe opening surrounded by the first layer patterns. In this embodiment,the photo resist pattern 47 formed in one opening has multiple patterns.In some embodiments, the photo resist pattern 47 includes n×m matrixpattern, where n and m are natural numbers and n×m≠1. Distances ofspaces between adjacent multiple patterns are equal to or smaller than ahalf of either of S1 or S2 based on the directions of the spaces in someembodiments. In some embodiments, a distances of a space betweenadjacent patterns along the X direction is equal to or smaller than ahalf of the distance S1, and a distances of a space between adjacentpatterns along the Y direction is equal to or smaller than a half of thedistance S2.

FIG. 11 shows a cross sectional view of a semiconductor device accordingto embodiments of the present disclosure.

As shown in FIG. 11, one or more underlying electronic devices 105 areformed over a substrate 100. In some embodiments, the substrate 100 is asilicon substrate. Alternatively, the substrate may comprise anotherelementary semiconductor, such as germanium; a compound semiconductorincluding Group IV-IV compound semiconductors such as SiC and SiGe,Group III-V compound semiconductors such as GaAs, GaP, GaN, InP, InAs,InSb, GaAsP, AlGaN, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; orcombinations thereof. Amorphous substrates, such as amorphous Si oramorphous SiC, or an insulating material, such as silicon oxide may alsobe used as the substrate. In some embodiments, the underlying electronicdevices 105 are transistors, such as planar transistors, fin fieldeffect transistors and gate-all-around transistors.

As shown in FIG. 11, a first interlayer dielectric (ILD) layer 110 isformed over the underlying electronic devices 105. Then, firstconductive wiring patterns 115 are formed on or in the upper surface ofthe first ILD layer 110. One or more vias (not shown) are formed in thefirst ILD layer 110. Then, a second ILD layer 120 is formed over thefirst conductive wiring patterns 125. Then, second conductive patterns125 are formed on or in the upper surface of the second ILD layer 120.Further, a third ILD layer 130 is formed over second conductive wiringpatterns 125. Then, third conductive patterns 135 are formed on or inthe upper surface of the third ILD layer 130. Further, a fourth ILDlayer 140 is formed over third conductive wiring patterns 135. Formingan ILD layer and conductive wiring patterns is repeated, thereby formingthe n-th ILD layer, where 4<n<20 in some embodiments.

The ILD layers include silicon oxide, SiOCN, SiCO, SiCN, fluorine-dopedsilicate glass (FSG), or a low-k dielectric material, or any othersuitable dielectric materials. The ILD layers may be formed by chemicalvapor deposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), or other suitable film forming processes. Theconductive wiring patterns include metallic material, such as Al, Cu,AlCu, W, Co, Ti, Ta, Ni, silicide, TiN or TaN, or any suitablematerials. The conductive material can be formed by CVD, PVD, ALD,molecular beam epitaxy (MBE), electro plating, or other suitable filmforming processes.

In some embodiments of the present disclosure, after at least one of theILD layers is formed, the aforementioned planarization operation usingreflowed photo resist pattern is performed to planarize the given ILDlayer. In some embodiments, one or more line-shaped protrusions asdescribe above are formed on the upper surface of the ILD layer.Further, in some embodiments, the conductive wiring pattern subsequentlyformed on the ILD layer covers at least a part of the line-shapedprotrusions.

It will be understood that not all advantages have been necessarilydiscussed herein, no particular advantage is required for allembodiments or examples, and other embodiments or examples may offerdifferent advantages.

According to the embodiments of the present disclosure, it is possibleto obtain a higher flatness after a resist etch-back operation. Sincethe self-align reflow process is utilized, more overlay margin betweenthe photo resist pattern for the resist etch-back and the underlyingpattern can be obtained.

In accordance with one aspect of the present disclosure, in a method ofmanufacturing a semiconductor device, a first layer having an opening isformed over a substrate. A second layer is formed over the first layerand the substrate. A photo resist pattern is formed over the secondlayer above the opening of the first layer. The photo resist pattern isreflowed by a thermal process. An etch-back operation is performed toplanarize the second layer. In one or more of the foregoing andfollowing embodiments, the thermal process is performed at a temperaturein a range from 150° C. to 200° C. In one or more of the foregoing andfollowing embodiments, the thermal process is performed at a temperaturein a range from 170° C. to 180° C. In one or more of the foregoing andfollowing embodiments, the thermal process is performed for a timeduration in a range from 30 seconds to 120 seconds. In one or more ofthe foregoing and following embodiments, the thermal process isperformed for a time duration in a range from 40 seconds to 80 seconds.In one or more of the foregoing and following embodiments, after thesecond layer is formed, a step is formed in the second layer due to anedge of the opening of the first layer, and after the photo resistpattern is reflowed, the reflowed photo resist pattern contacts thestep. In one or more of the foregoing and following embodiments, afterthe photo resist pattern is reflowed, the reflowed photo resist patternfully covers a side wall of the step. In one or more of the foregoingand following embodiments, a slope of a steepest portion of the reflowedphoto resist pattern in contact with the side wall is in a range from10° to 20° with respect to a surface of the substrate. In one or more ofthe foregoing and following embodiments, the second layer comprises aupper surface and a lower surface connected by the step, the photoresist pattern is formed on the lower surface and no photo resistpattern is formed on the upper surface, and after the photo resistpattern is reflowed, no reflowed photo resist pattern is disposed on theupper surface. In one or more of the foregoing and followingembodiments, a distance between an edge of the opening of the firstlayer closest to the photo resist pattern and an edge of the photoresist pattern closest to the edge of the opening of the first layer isin a range from 100 nm to 2000 nm in plan view. In one or more of theforegoing and following embodiments, the distance is in a range from 200nm to 800 nm in plan view. In one or more of the foregoing and followingembodiments, after the reflowing, the reflowed photo resist patternoverlaps the first layer by an overlap amount. In one or more of theforegoing and following embodiments, the overlap amount is in a rangefrom 10 nm to 200 nm. In one or more of the foregoing and followingembodiments, the overlap amount is in a range from 20 nm to 100 nm. Inone or more of the foregoing and following embodiments, after thereflowing, the reflowed photo resist pattern is spaced apart from thefirst layer by a distance in plan view. In one or more of the foregoingand following embodiments, the distance is in a range from 10 nm to 200nm. In one or more of the foregoing and following embodiments, thedistance is in a range from 20 nm to 100 nm. In one or more of theforegoing and following embodiments, after the etch-back operation, aprotrusion of the second layer having a height in a range from 10 nm to100 nm is formed. In one or more of the foregoing and followingembodiments, wherein the protrusion is asymmetric in a cross section.

In accordance with another aspect of the present disclosure, in a methodof manufacturing a semiconductor device, in a method of manufacturing asemiconductor device, a first layer having first layer patterns and anopening surrounded by the first layer patterns is formed over asubstrate. A second layer is formed over the first layer and thesubstrate. A photo resist pattern is formed over the second layer abovethe opening of the first layer. The photo resist pattern is reflowed bya thermal process. An etch-back operation is performed to planarize thesecond layer. The photo resist pattern has a rectangular shape having along side and a short side, and a distance between the long side and oneof the first layer pattern facing the long side is greater than adistance between the short side and one of the first layer patternfacing the short side.

In accordance with one aspect of the present disclosure, in a method ofmanufacturing a semiconductor device, a plurality of first metal wiringpatterns are formed over a first dielectric layer. A second dielectriclayer is formed over the first metal wiring patterns. A photo resistpattern is formed over the second dielectric layer. The photo resistpattern is reflowed by a thermal process. An etch-back operation isperformed to planarize the second dielectric layer. A plurality ofsecond metal wiring patterns are formed over the planarized seconddielectric layer. The photo resist pattern is formed over the seconddielectric layer at a region under which no first metal wiring patternis formed.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A method of manufacturing a semiconductor device,the method comprising: forming a first layer having an opening over asubstrate; forming a second layer over the first layer and thesubstrate; forming a photo resist pattern over the second layer abovethe opening of the first layer; reflowing the photo resist pattern by athermal process; and performing an etch-back operation to planarize thesecond layer.
 2. The method of claim 1, wherein the thermal process isperformed at a temperature in a range from 150° C. to 200° C.
 3. Themethod of claim 1, wherein the thermal process is performed at atemperature in a range from 170° C. to 180° C.
 4. The method of claim 1,wherein the thermal process is performed for a time duration in a rangefrom 30 seconds to 120 seconds.
 5. The method of claim 1, wherein thethermal process is performed for a time duration in a range from 40seconds to 80 seconds.
 6. The method of claim 1, wherein: after thesecond layer is formed, a step is formed in the second layer due to anedge of the opening of the first layer, and after the photo resistpattern is reflowed, the reflowed photo resist pattern contacts thestep.
 7. The method of claim 6, wherein after the photo resist patternis reflowed, the reflowed photo resist pattern fully covers a side wallof the step.
 8. The method of claim 7, wherein a slope of a steepestportion of the reflowed photo resist pattern in contact with the sidewall is in a range from 10° to 20° with respect to a surface of thesubstrate.
 9. The method of claim 6, wherein: the second layer comprisesa upper surface and a lower surface connected by the step, the photoresist pattern is formed on the lower surface and no photo resistpattern is formed on the upper surface, and after the photo resistpattern is reflowed, no reflowed photo resist pattern is disposed on theupper surface.
 10. The method of claim 1, wherein a distance between anedge of the opening of the first layer closest to the photo resistpattern and an edge of the photo resist pattern closest to the edge ofthe opening of the first layer is in a range from 100 nm to 2000 nm inplan view.
 11. The method of claim 1, wherein after the reflowing, thereflowed photo resist pattern overlaps the first layer by an overlapamount.
 12. The method of claim 11, wherein the overlap amount is in arange from 10 nm to 200 nm.
 13. The method of claim 11, wherein theoverlap amount is in a range from 20 nm to 100 nm.
 14. The method ofclaim 1, wherein after the reflowing, the reflowed photo resist patternis spaced apart from the first layer by a distance in plan view.
 15. Themethod of claim 14, wherein the distance is in a range from 10 nm to 200nm.
 16. The method of claim 14, wherein the distance is in a range from20 nm to 100 nm.
 17. The method of claim 1, wherein after the etch-backoperation, a protrusion of the second layer having a height in a rangefrom 10 nm to 100 nm is formed.
 18. The method of claim 17, wherein theprotrusion is asymmetric in a cross section.
 19. A method ofmanufacturing a semiconductor device, the method comprising: forming afirst layer having first layer patterns and an opening surrounded by thefirst layer patterns over a substrate; forming a second layer over thefirst layer and the substrate; forming a photo resist pattern over thesecond layer above the opening of the first layer; reflowing the photoresist pattern by a thermal process; and performing an etch-backoperation to planarize the second layer, wherein the photo resistpattern has a rectangular shape having a long side and a short side, adistance between the long side and one of the first layer pattern facingthe long side is greater than a distance between the short side and oneof the first layer pattern facing the short side.
 20. A method ofmanufacturing a semiconductor device, the method comprising: forming aplurality of first metal wiring patterns over a first dielectric layer;forming a second dielectric layer over the plurality of first metalwiring patterns; forming a photo resist pattern over the seconddielectric layer; reflowing the photo resist pattern by a thermalprocess; performing an etch-back operation to planarized the seconddielectric layer; and forming a plurality of second metal wiringpatterns over the planarized second dielectric layer, wherein the photoresist pattern is formed over the second dielectric layer at a regionunder which no first metal wiring pattern is formed.